| J Tanner Agri Services Ltd | Construction | 2015 |
| J. L. Thayer Electrical Ltd | Construction | 2016 |
| J.A.M & Toast Limited | Professional & scientific | 2026 |
| J.A.M. Online Limited | Administrative & support | 2009 |
| J.B Tree Services Ltd | Administrative & support | 2025 |
| J.W.H. Buckle and Sons Limited | Construction | 2002 |
| JAG Home Services Ltd | Construction | 2019 |
| Jamie Hampton Flooring Limited | Construction | 2019 |
| Jane John Limited | Professional & scientific | 2004 |
| Jarman Space Enterprises Ltd | Manufacturing | 2024 |
| Jaycee Ltd | Manufacturing | 2006 |
| Jaze DE Luxe Studio Limited | Other services | 2025 |
| Jazzbones Creative Limited | Information & communication | 2008 |
| JC3D Prints Ltd | Manufacturing | 2023 |
| JCM10 Ltd | Transport & logistics | 2026 |
| JD Little Decorating Ltd | Construction | 2026 |
| JDH Auto Services Limited | Wholesale & retail | 2013 |
| JE Hubbard Motor Company Ltd | Wholesale & retail | 2019 |
| Jeff Sainsbury Tours Limited | Administrative & support | 1999 |
| JEM Body Solutions Ltd | Health & social care | 2023 |
| Jensen Wealth Management Limited | Professional & scientific | 2017 |
| Jepico Holdings Limited | Financial services | 2018 |
| Jess to Success Ltd | Real estate | 2024 |
| Jethro Tull Production Limited | Arts & recreation | 1996 |
| Jethrow Wiltshire Plumbing & Heating Ltd | Construction | 2017 |
| Jezzinc Ltd | Other services | 2011 |
| JF Doors and Windows Limited | Construction | 2017 |
| JFS Property Group Limited | Real estate | 2026 |
| Jigsaw Alternative Provision Limited | Education | 2023 |
| Jinchi Limited | Information & communication | 2015 |
| JIS Western Developments LLP | | 2008 |
| JJ Bricklaying & Building Limited | Construction | 2020 |
| Jmmc Property Ltd | Real estate | 2020 |
| JMS Carpets & Flooring Ltd | Wholesale & retail | 2021 |
| Jobella Limited | Financial services | 2025 |
| Joe's GOT Wood Limited | Agriculture & fishing | 2017 |
| John & Sons Properties PVT Limited | Real estate | 2023 |
| John Fletcher Ltd | Information & communication | 2020 |
| John Kimpton Properties Limited | Real estate | 2021 |
| John Matthews Consultancy Services Ltd | Professional & scientific | 2022 |
| John Mchugh (Stretford) Limited | Wholesale & retail | 1959 |
| Johnnsons Ltd | Administrative & support | 2020 |
| Jolly Wild Ltd | Arts & recreation | 2020 |
| JON Wiltshire Limited | Arts & recreation | 2024 |
| Jonathan Skull Limited | Wholesale & retail | 2007 |
| Jones Dane Ltd | Wholesale & retail | 2024 |
| Jonholdco Ltd | Financial services | 2022 |
| Jordan Developments Group Limited | Real estate | 2018 |
| Josh Heydon Solutions Limited | Professional & scientific | 2017 |
| Joy KIN Investments Ltd | Real estate | 2021 |
| JPF Exterior Cleaning Services Ltd | Administrative & support | 2023 |
| JR Building and Maintenance Ltd | Construction | 2025 |
| JR Rugs and Flooring Ltd | Wholesale & retail | 2024 |
| JRB Property Solutions Limited | Real estate | 2023 |
| JSB Film Supplies Ltd | Wholesale & retail | 2011 |
| JT Real Estate Limited | Real estate | 2021 |
| Jtek Auto Ltd | Wholesale & retail | 2021 |
| Judmedia Limited | Information & communication | 2019 |
| Jugo Energy Management Ltd | Professional & scientific | 2015 |
| Juliart Ltd | Extraterritorial | 2008 |
| Just Cats Boarding Cattery Ltd | Other services | 2003 |
| K & C Building Solutions Ltd | Construction | 2018 |
| K 4 Kitchens Limited | Wholesale & retail | 2002 |
| K M Elite Ltd | Wholesale & retail | 2021 |
| K-Tec Food Machinery Limited | Wholesale & retail | 2021 |
| K9 Thrive Ltd | Other services | 2025 |
| Kanata Cleaning Services Limited | Administrative & support | 2025 |
| Karahasan Limited | Wholesale & retail | 2025 |
| Kasimpas Ltd | Hospitality | 2025 |
| Kasm Drylining Ltd | Construction | 2021 |
| Kate Hatfield Consulting Limited | Professional & scientific | 2010 |
| KCM Developments Limited | Construction | 2004 |
| Keeva Travel Limited | Administrative & support | 2017 |
| Keiron Starns Care Agency Limited | Health & social care | 2011 |
| Kendi Care Ltd | Health & social care | 2019 |
| Kenilworth Court Management Company (Melksham) Limited | Households | 1989 |
| Kerr Properties (SW) Limited | Households | 2023 |
| Kevin Pocock Utilities Limited | Construction | 2013 |
| King's Court Estate and Trust Planning Limited | Professional & scientific | 2014 |
| King's Court Financial Planning LLP | | 2002 |
| Kingsford Consultancy Services Limited | Professional & scientific | 2016 |
| Kington Deluxe Toilet Hire Limited | Administrative & support | 2020 |
| Kington Deluxe Toilet Hire SW Ltd | Administrative & support | 2025 |
| Kington Events SW Ltd | Other services | 2025 |
| Kington Filming Ltd | Administrative & support | 2026 |
| Kington Group Limited | Financial services | 2025 |
| Kington WET Waste Ltd | Water & waste | 2025 |
| Kiswa Enterprises Limited | Wholesale & retail | 2025 |
| KL Auto Repair Ltd | Wholesale & retail | 2025 |
| Knees Engineering Limited | Manufacturing | 1958 |
| Kngfield Ltd | Other services | 2023 |
| Knockvaragh Investments Limited | Financial services | 2017 |
| Knot and Grain (Wiltshire) Ltd | Manufacturing | 2023 |
| Kranti Farm Ltd | Hospitality | 2021 |
| Kung FU Academy Ltd | Education | 2017 |
| L & J Collective Limited | Professional & scientific | 2008 |
| L Davis Media Limited | Professional & scientific | 2021 |
| L H Servicing & Repair Ltd | Wholesale & retail | 2024 |
| L&C Skin Ltd | Wholesale & retail | 2026 |
| L&T Retail Limited | Wholesale & retail | 2022 |